The site plan was posted to the AULCC's website. The building elevations are in color, and also if you scroll down to the last pages of the site plan there's a couple more images of it.
The elevations show some signage calling it "Red River Tower".
354 feet 4 inches - mechanical penthouse roof
332 feet 4 inches - main roof parapet
326 feet 4 inches - main roof slab
315 feet - 29th floor
ftp://ftp.ci.austin.tx.us/ATD_AULCC/...nt_PLAN_02.pdf